module_utils: require X_OK when checking cwd sanity

[seirl]

SUMMARY

Every time an Ansible module is run, it checks that it is running from a
"sane" working directory, a.k.a where it has the permission to be. This
is because when running commands, it might temporarily change its
working directory, then later restore pop the cwd to the previous one.

Therefore, if the module is not run from a working directory where it
has the permission to be, the module will execute fine, but then fail
when trying to restore to the previous directory.

Up until now the way this cwd "sanity" was checked was by checking for
the F_OK and R_OK permissions, which respectively check that the
directory exists and is readable. However, this is actually not
sufficient to check whether you can cwd to it! You also need to check
for X_OK, which for directories mean that the directory is searchable.

See for example:

>>> cwd = os.getcwd()
>>> cwd
'/root'
>>> os.access(cwd, os.F_OK | os.R_OK)
True
>>> os.access(cwd, os.F_OK | os.R_OK | os.X_OK)
False
>>> os.chdir(cwd)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
PermissionError: [Errno 13] Permission denied: '/root'

Basically, this means that Ansible will fail every time you run a
"become" command from a directory with the mode o+r-x.

This commit fixes this issue by adding a requirement for X_OK when
checking the sanity of the current working directory.

ISSUE TYPE

• Bugfix Pull Request

COMPONENT NAME

module_utils

[seirl]

The CI errors look like false alarms.

[seirl]

Closing and re-opening to trigger a new CI build, as explained in https://docs.ansible.com/ansible/latest/dev_guide/testing.html#rerunning-a-failing-ci-job

[seirl]

/rebuild_failed

[jimi-c]

Hi @seirl, could you please add a changelog entry to this PR, as well as an integration test to show the new behavior is correct?

Thanks!

[seirl]

Sure, could you point out where this test would fit? The commit that introduces this function doesn't have a test attached to it, so I'm not sure where the previous behavior was tested.

[seirl]

I added the changelog entry.

[webknjaz]

The branch is too old for the CI to pick it up. Needs rebase.

[webknjaz]

@mattclay @sivel this is an example PR that #84375 / #84402 would've helped with.

[webknjaz]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[webknjaz]

Restarting because the bot keeps sticking this into the review queue and doesn't persist the manually set needs_rebase label.